This invention relates to compositions comprising a benzodiazepine and certain analgesic agents which enhance the binding of said benzodiazepine to central benzodiazepine receptors. More particularly it is concerned with compositions of the foregoing type which achieve a potentiation of said benzodiazepine receptor binding in mammals, including man, to which they are administered.
The benzodiazepines, a unique class of anxiolytic, anticonvulsant and sedative-hypnotic drugs, are the most widely prescribed "minor tranquilizers" in use today. When administered via the oral route, they become widely distributed throughout the body, particularly in lipid-rich tissues such as adipose and brain. The publication "Sleeping Pills, Insomnia and Medical Practice, Report of a Study of the Institute of Medicine", National Academy of Sciences, Washington D.C., 1979, reports that pharmacologically active metabolites of the benzodiazepines are frequently long-lived. The impairment in "next-day" functioning when benzodiazepines are used as hypnotics is considered attributable to the delay in excretion of said metabolites. Still further, cumulative dose effects have been disclosed in the above-cited report following long-term use of benzodiazepines. Other problems associated with use of benzodiazepines are physical withdrawal symptoms after abrupt cessation of moderate to high doses and interaction with other central nervous system (CNS) depressants, especially alcohol.
Enhancement of benzodiazepine binding in vitro and enhancement of the pharmacological effects of diazepam in vivo by N.sup.6 -[2-(4-chlorophenyl)]-bicyclo-[2.2.2]-octyl-(3)-adenosine (EMD 28422) has been reported by Skolnick et al., Pharmacol. Biochem. & Behavior, 12, 685-689 (1980). Williams et al., European J. Pharmacol. 56, 273-276 (1979) found that Avermectin B.sub.1a, a macrocyclic lactone disaccharide anthelmintic agent, enhance the in vitro binding of diazepam to rat and mouse brain membranes.
Other substances such as divalent nickel ions, gamma-aminobutyric acid and 5-aminomethyl-3-hydroxyisoxazole have also been reported to enhance in vitro binding of diazepam.
It is, therefore, apparent that development of a formulation and/or method which permits use of smaller doses of a benzodiazepine but which achieves at least the same level of effectiveness thereof is highly desirable.